Increase signal stack size on 32-bit to 16kB.

snprintf to a buffer of length PATH_MAX consumes about 7kB of stack.

Bug: http://b/35858739
Test: bionic-unit-tests --gtest_filter="*big_enough*"
Change-Id: I34a7f42c1fd2582ca0d0a9b7e7a5290bc1cc19b1

2 files changed, 22 insertions, 15 deletions

diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index b17029968..6faf5a4ff 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -141,13 +141,11 @@ static inline __always_inline bionic_tls& __get_bionic_tls() {
 
 __LIBC_HIDDEN__ void pthread_key_clean_all(void);
 
-#if defined(__LP64__)
-// SIGSTKSZ is not big enough for 64-bit arch.
-// See https://code.google.com/p/android/issues/detail?id=187064.
+// SIGSTKSZ (8kB) is not big enough.
+// snprintf to a stack buffer of size PATH_MAX consumes ~7kB of stack.
+// Also, on 64-bit, logging uses more than 8kB by itself:
+// https://code.google.com/p/android/issues/detail?id=187064
 #define SIGNAL_STACK_SIZE_WITHOUT_GUARD_PAGE (16 * 1024)
-#else
-#define SIGNAL_STACK_SIZE_WITHOUT_GUARD_PAGE SIGSTKSZ
-#endif
 
 /*
  * Traditionally we gave threads a 1MiB stack. When we started
diff --git a/tests/pthread_test.cpp b/tests/pthread_test.cpp
index 024a6754e..4fb15ad8a 100755
--- a/tests/pthread_test.cpp
+++ b/tests/pthread_test.cpp
@@ -1888,17 +1888,26 @@ static volatile bool signal_handler_on_altstack_done;
 
 static void SignalHandlerOnAltStack(int signo, siginfo_t*, void*) {
   ASSERT_EQ(SIGUSR1, signo);
-  // Check if we have enough stack space for unwinding.
-  int count = 0;
-  _Unwind_Backtrace(FrameCounter, &count);
-  ASSERT_GT(count, 0);
-  // Check if we have enough stack space for logging.
-  std::string s(2048, '*');
-  GTEST_LOG_(INFO) << s;
-  signal_handler_on_altstack_done = true;
+  {
+    // Check if we have enough stack space for unwinding.
+    int count = 0;
+    _Unwind_Backtrace(FrameCounter, &count);
+    ASSERT_GT(count, 0);
+  }
+  {
+    // Check if we have enough stack space for logging.
+    std::string s(2048, '*');
+    GTEST_LOG_(INFO) << s;
+    signal_handler_on_altstack_done = true;
+  }
+  {
+    // Check if we have enough stack space for snprintf to a PATH_MAX buffer, plus some extra.
+    char buf[PATH_MAX + 2048];
+    ASSERT_GT(snprintf(buf, sizeof(buf), "/proc/%d/status", getpid()), 0);
+  }
 }
 
-TEST(pthread, big_enough_signal_stack_for_64bit_arch) {
+TEST(pthread, big_enough_signal_stack) {
   signal_handler_on_altstack_done = false;
   ScopedSignalHandler handler(SIGUSR1, SignalHandlerOnAltStack, SA_SIGINFO | SA_ONSTACK);
   kill(getpid(), SIGUSR1);